In a double-belt press, each of two belts is guided along respective arrays of support rollers and the material to be subjected to the pressing or conveying operation of the double-belt system is engaged between the belts and conveyed in succession between the rolls of the support roll pairs.
The adjustment of the gap width of the press and hence the spacing between pairs of support rolls has been effected in accordance with known techniques by relative adjustment of the upper and lower machine frames upon which the support rolls were mounted and/or by individual adjustments of the support rolls.
In the case of a plurality of support roll pairs, where each roll pair must be adjusted under load to the correct gap width, it has been necessary to provide extensive measurement and control devices and procedures for such adjustment.
If one abandons the effort to adjust the individual gap widths of each individual roll pair and merely monitors the final thickness of the pressed produce and adjusts the gap widths in a feedback response, the machine may not operate in its most efficient and optimum manner since the various roll pairs themselves may not operate at optimum working points.